[Pw_forum] U for Oxygen
Matteo Cococcioni
matteo at umn.edu
Tue Aug 4 18:52:01 CEST 2009
this is what comes out from the calculation (U(O) > U(Ni)). whether it's
reasonable to apply U on O or not, I'm not sure.
I think the U shouldn't be used on states that are completely occupied.
Matteo
ali kazempour wrote:
> Dear Matteo
> This means that hubbard parameter for oxygen is large (grater than
> Ni). Is it correct or originate from another challenge?
> thanks
>
> Ali Kazempour
> Physics department, Isfahan University of Technology
> 84156 Isfahan, Iran. Tel-1: +98 311 391 3733
> Fax: +98 311 391 2376 Tel-2: +98 311 391 2375
>
> --- On *Tue, 8/4/09, Matteo Cococcioni /<matteo at umn.edu>/* wrote:
>
>
> From: Matteo Cococcioni <matteo at umn.edu>
> Subject: Re: [Pw_forum] U for Oxygen
> To: "PWSCF Forum" <pw_forum at pwscf.org>
> Date: Tuesday, August 4, 2009, 6:59 AM
>
>
>
> Dear Ali,
>
>
>
> ali kazempour wrote:
> > Dear Matteo
> > I used your comment and followed your example for NiO and I
> succeed
> > to get U for TiO2. But in file Ur16.out I see three column .
> >
>
> I don't have any three column section in any of my files. so if
> you want
> me to help you you have to report at least a section of your output
> file. This is a good habit actually in consideration of the fact that
> this is not a private conversation (I would have asked you in any
> case
> as I don't remember by heart the format of any file) between me
> and you
> but a message to the forum and you want other people to understand
> what you are saying.
>
> > The first is number of atom in supercell , second is U value for Ni
> > atom and I don,t know the third? does the third belong to U value
> > for Oxygen or not? Because the third column kas big value?
> >
> >
> > another question is for isolated atom Hubbard parameter. What do
> you
> > expect about the value of U for Isolated atom? Is this big value
> > (greater than 10 eV) or it would be tiny value?
> >
>
> I think it will be meaningless for the reasons I explained in my last
> email. To obtain a meaningful number for the isolated atom you
> probably
> have to abandon the idea to use a perturbation in the potential and
> change instead the number of electrons directly. This means you will
> have to do calculations on atoms having fractional charges which
> requires additional corrections if you use a code designed for
> periodic
> systems (crystals). However I have never done this isolated atom
> calculation of U before so I don't have more details about it.
> I see (from a private email) you are thinking of computing U for the
> isolated atom and to obtain a value for the crystal just by
> dividing by
> the epsilon_inft. the method is proposed in
>
> http://link.aps.org/doi/10.1103/PhysRevB.74.045202
>
> (which I haven't re-read yet).
>
> I see a couple of problems:
>
> 1) (not important for ZnO). suppose you have Fe3O4 with Fe2+ and
> Fe3+.
> these Fe ions likely have different U. how do you obtain
> a different number from the atomic code? would you do the calculation
> for isolated Fe2+ and Fe3+?
>
> 2) how do you get epsilon? since it's a linear response property I
> don't
> think its calculation is any cheaper than the direct calculation of U.
>
> regards,
>
> Matteo
>
> > should we choose for running the script for isolated atom only
> gamma
> > point or we have to choose a fine mesh?
> > thanks a lot
> >
> >
> > Ali Kazempour
> > Physics department, Isfahan University of Technology
> > 84156 Isfahan, Iran. Tel-1: +98 311 391 3733
> > Fax: +98 311 391 2376 Tel-2: +98 311 391 2375
> >
> > --- On *Sun, 8/2/09, Matteo Cococcioni /<matteo at umn.edu
> </mc/compose?to=matteo at umn.edu>>/* wrote:
> >
> >
> > From: Matteo Cococcioni <matteo at umn.edu
> </mc/compose?to=matteo at umn.edu>>
> > Subject: Re: [Pw_forum] occupation
> > To: "PWSCF Forum" <pw_forum at pwscf.org
> </mc/compose?to=pw_forum at pwscf.org>>
> > Date: Sunday, August 2, 2009, 8:31 AM
> >
> >
> > Dear Ali,
> >
> > 1, -1, 0 are just spin indexes to tell the code what is the
> relative
> > magnetization of the atoms (parallel, antiparallel, or none). if
> > your system is non magnetic put all 0. or set magn = .false.
> and put
> > nothing.
> > you should look at the examples on Fe and Si as well and
> learn from
> > there by comparison.
> >
> > Matteo
> >
> >
> >
>
>
> --
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> Matteo Cococcioni
> Department of Chemical Engineering and Materials Science,
> University of Minnesota
> 421 Washington Av. SE
> Minneapolis, MN 55455
> Tel. +1 612 624 9056 Fax +1 612 626 7246
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
>
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--
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
Matteo Cococcioni
Department of Chemical Engineering and Materials Science,
University of Minnesota
421 Washington Av. SE
Minneapolis, MN 55455
Tel. +1 612 624 9056 Fax +1 612 626 7246
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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